This standard specifies the methods for determining sugars using high pressure liquid chromatography, Rhine-Eynon method and magnesium-colorimetry. Method 1 of this standard is applicable to the determination of various sugars in infant formula and milk powder; Method 2 is applicable to the determination of lactose, sucrose and total sugar in whole milk powder, whole fat sweetened milk powder, skim milk powder and other milk powder products containing only lactose and sucrose in the total sugar; Method 3 is applicable to the determination of sucrose in infant formula and milk powder. GB/T 5413.5-1997 Determination of lactose, sucrose and total sugar in infant formula and milk powder GB/T5413.5-1997 Standard download decompression password: www.bzxz.net

GB/T5413.5—1997
The determination of sugar in food usually adopts the redox titration method, but the presence of other reducing sugars will interfere with the determination. This standard provides three determination methods, of which method one, high pressure liquid chromatography, and method two, enzyme colorimetry, avoid the interference of reducing sugars and have higher accuracy. Method one can determine various sugars at the same time. Method three adopts the GB/T16286-1996 method. Considering that the traditional redox titration method has a higher accuracy in determining lactose and sucrose in the absence of interference from other reducing sugars, and the required instruments and equipment are simple, most laboratories are accustomed to using this method. Therefore, the "Lane-Eynon method\(Lane andEynor'sMethod) is given as Method 2.
Method 1 of this standard is the arbitration method.
This series of standards replaces GB5413-85 from the date of implementation. This standard is proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Dairy Standardization Center. The responsible drafting unit of this standard is the National Dairy Quality Supervision and Inspection Center. The participating drafting units of this standard are: Food Hygiene Supervision and Inspection Institute of the Ministry of Health, Zhejiang Light Industry Research Institute, Harbin Morinaga Dairy Co., Ltd., and Nestlé (China) Investment Services Co., Ltd. The main drafters of this standard are: Wang Yun, Yang Jinbao, Li Yuxian, and Wang Xinxiang. 240
National Standard of the People's Republic of China
Infant formula foods and milk powder
Determination of lactose, sucrose and total sugars contents1Scope
GB/T 5413. 5---1997
Replaces GB5413-85
This standard specifies the methods for determining sugars by high pressure liquid chromatography, Rhine-Eynon method and enzyme-colorimetry. Method 1 of this standard is applicable to the determination of various sugars in infant formula and milk powder; Method 2 is applicable to the determination of lactose, sucrose and total sugar in whole milk powder, whole fat sweetened milk powder, skimmed milk powder and other milk powder products containing only lactose and sucrose in the total sugar; Method 3 is applicable to the determination of sucrose in infant formula and milk powder. 2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1 6286--1996 Method for determination of sucrose in food Enzyme-colorimetry Method 1 High pressure liquid chromatography
3 Method summary
If infant food contains multiple sugars, they can be separated using the μ-carbohydrate column or amino column (Lichrosorb-NHz column) of high pressure liquid chromatography, and the refractive index of each sugar solution can be detected using a differential refractometer. This refractive index is proportional to its concentration. 4 Reagents
All reagents, if not specified, are analytically pure. All experimental water, if not specified otherwise, is grade tertiary water. 4.1 Clarifying agent: copper sulfate, mass fraction 7%. Sodium hydroxide, mass fraction 4%. 4.2 Acetonitrile.
4.3 Standard solution
4.3.1 Standard sugar stock solution, 10 mg/mL. Accurately weigh 1 g of the standard sample of the sugar to be tested, dissolve it in water, dilute it with water to a 100 mL volumetric flask, and make up to volume. 4.3.2 Standard push sugar working solution, 4 mg/mL.
Pipette 4 mL of stock solution, place in a 10 mL volumetric flask, and dilute to scale with acetonitrile. 5 Instruments
Common laboratory instruments and:
5.1 High pressure liquid chromatograph with carbohydrate analysis column or amino column. Approved by the State Administration of Technical Supervision on May 28, 1997 and implemented on September 1, 1998
6 Operating steps
6.1 Sample solution preparation
GB/T 5413. 5---1997
Accurately weigh about 2 g of sample, add 30 mL of water to dissolve, transfer to a 100 mL volumetric flask, add clarifier copper sulfate (4.1) 10 mL, sodium hydroxide (4.1) 4 mL, shake, add water to scale, let stand for half an hour, and filter. Take 4mL of sample mother solution and place it in a 10mL volumetric flask. Add acetonitrile to the volume and filter it through a 0.45μm filter. The filtrate is reserved. 6.2 High-pressure liquid chromatography working conditions:
R401 differential refractive index detector:
30cm×4.6mm inner diameter-carbohydrate analysis column (jacket insulation 20℃) Mobile phase: acetonitrile/water = 85/15
Mobile phase flow rate: 0.5mL/min
6.3 Injection
After the instrument is stable, use a syringe or injection valve to inject 50uL of standard sample solution for a total of 4 times, record the retention time, measure the peak height, discard the first data, take the average peak height of the last three, and inject 50μL four times to get the average peak height. 7 Analysis of the expression of the nest
Sugar content in the sample (g/100g)
Where: C standard sugar solution concentration, mg/mL; H-average peak height of sugar in the sample;
H\--peak height of standard sugar solution;
mass of the sample, g.
X 100 -
4×1000
25C× H
Note: If it is necessary to determine other sugars contained in the sample at the same time, add 1g of various sugars to the standard sugar solution, inject as before, record the retention time of various sugars, and calculate each value according to the above formula.
8 Allowable difference
The difference between the two measured values ​​of the same sample shall not exceed 5% of the average value of the two measurements. Method 2 Determination of lactose, sucrose and total sugar (Rhine-Eynon method) 9 Method Summary
Lactose: After the sample is deproteinized, the sample is directly titrated with the calibrated Fehling's solution under heating conditions. The lactose in the sample solution reduces the divalent copper in the Fehling's solution to cuprous oxide. With methylene blue as the indicator, when the end point is slightly excessive, lactose reduces the blue oxidized methylene blue to colorless reduced methylene blue. Calculate the lactose content based on the volume consumed by the sample solution. Sucrose: After the sample is deproteinized, the sucrose in the sample is hydrolyzed with hydrochloric acid to glucose and fructose with reducing ability, and then determined as reducing sugar. The difference between the converted sugar before and after hydrolysis multiplied by the corresponding coefficient is the sucrose content. Total sugar: The sum of lactose and sucrose.
10 Reagents
All reagents, if the specifications are not specified, are analytically pure. All experimental water, if no other requirements are specified, is grade tertiary water. 10.1 Fehling's solution (liquid A and liquid B)
10.1.1 Liquid A: Take 34.639g of copper sulfate, dissolve it in water, add 0.5mL of concentrated sulfuric acid, and add water to 500mL. 242
GB/T 5413. 5--1997
10.1.2 Liquid B: Take 173g of potassium sodium tartrate and 50g of sodium hydroxide and dissolve them in water, dilute to 500mL, let it stand for two days and then filter. 10.2 Methylene blue solution: 10g/L.
10.3 Hydrochloric acid solution: volume ratio 1:1.
10.4 Phenolyl solution: 0.5g phenolphthalein is dissolved in 75mL 95% ethanol by volume, and 20mL water is added, and then about 0.1mol/L sodium hydroxide solution is added until it turns pink immediately after adding one drop, and then water is added to make up to 100ml. 10.5 Sodium hydroxide solution: c(NaOH) is 300g/L. Take 300g sodium hydroxide and dissolve it in 1000mL water. 10.6 Lead acetate solution: c(PbAc2) is 200g/L. Take 20g lead acetate and dissolve it in 100mL water. 10.7 Potassium oxalate-disodium hydrogen phosphate solution: Take 3g potassium oxalate and 7g disodium hydrogen phosphate and dissolve them in 100mL water 1.11 Instruments
Common physical and chemical laboratory instruments.
12 Operation steps and calculation of results
12.1 Standardization of Fehling's solution
12.1.1 Standardization with lactose
12.1.1.1 Weigh about 0.75g (accurate to 0.2mg) of lactose standard sample that has been dried in an oven at 92～~94℃ for 2h, dissolve it in water and dilute it to 250mL. Pour this lactose solution into a 50mL burette for titration. 12.1.1.2 Pre-titration: Take 10mL of Fehling's solution (5mL each of solution A and solution B) into a 250mL conical flask. Add 20mL of distilled water, release 15mL of lactose solution from the burette into the conical flask, place it on an electric stove and heat it to make it boil within 2min. After boiling, turn down the flame and keep boiling for 15s, add 3 drops of methylene blue solution (10.2) Continue to drip lactose solution until the blue color completely fades away, and read the milliliters of lactose used.
12.1.1.3 Accurate titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, and then add 0.5-1.0mL less lactose solution than the prepared titration amount, place it on an electric stove, and let it boil within 2 minutes. After boiling, turn down the flame and maintain the boiling state for 2 minutes, add 3 drops of methylene blue solution, and then continue to drip lactose solution (drop by drop slowly), and the end point is when the blue color completely fades away. Use this titration amount as the basis for calculation (when measuring sucrose at the same time, this is the titration amount before conversion). 12.1.1.4 Calculate the lactose correction value (f1) of Fehling's solution when determining lactose according to formula (2) and (3): At - ×m× 1000 = 4 ×V, × m250
4×V,×m
actual lactose amount measured, mg,
where: A,\—
Vi——the amount of lactose solution consumed during titration, mL; m
the mass of lactose weighed, g;
the lactose amount obtained by looking up the milliliters of lactose solution titrated in Table 1, mg. (2)
(3)
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)3 Accurate titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, and then add 0.5-1.0mL less lactose solution than the prepared titration amount, put it on an electric stove, let it boil within 2 minutes, turn down the flame after boiling, maintain the boiling state for 2 minutes, add 3 drops of methylene blue solution, and then continue to drip lactose solution (drop by drop slowly), and the end point is when the blue color completely fades. Use this titration as the basis for calculation (when measuring sucrose at the same time, this is the titration before conversion). 12.1.1.4 Calculate the lactose correction value (f1) of Fehling's solution when determining lactose according to formula (2) and (3): At - ×m× 1000 = 4 ×V, × m250
4×V,×m
actual lactose amount measured, mg,
where: A,\—
Vi——the amount of lactose solution consumed during titration, mL; m
the mass of lactose weighed, g;
the lactose amount obtained by looking up the milliliters of lactose solution titrated in Table 1, mg. (2)
(3)
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted. wwW.bzxz.Net
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)3 Accurate titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, and then add 0.5-1.0mL less lactose solution than the prepared titration amount, put it on an electric stove, let it boil within 2 minutes, turn down the flame after boiling, maintain the boiling state for 2 minutes, add 3 drops of methylene blue solution, and then continue to drip lactose solution (drop by drop slowly), and the end point is when the blue color completely fades. Use this titration as the basis for calculation (when measuring sucrose at the same time, this is the titration before conversion). 12.1.1.4 Calculate the lactose correction value (f1) of Fehling's solution when determining lactose according to formula (2) and (3): At - ×m× 1000 = 4 ×V, × m250
4×V,×m
actual lactose amount measured, mg,
where: A,\—
Vi——the amount of lactose solution consumed during titration, mL; m
the mass of lactose weighed, g;
the lactose amount obtained by looking up the milliliters of lactose solution titrated in Table 1, mg. (2)
(3)
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)0mL lactose solution is placed on an electric stove and boiled within 2 minutes. After boiling, turn down the flame and keep boiling for 2 minutes. Add 3 drops of methylene blue solution and then continue to drip lactose solution (drop by drop). The end point is when the blue color completely fades away. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration before conversion). 12.1.1.4 Calculate the lactose correction value (f1) of Fehling's solution when determining lactose according to formula (2) and (3): At - ×m× 1000 = 4 ×V, × m250
4×V,×m
actual lactose amount measured, mg,
where: A,\—
Vi——the amount of lactose solution consumed during titration, mL; m
the mass of lactose weighed, g;
the lactose amount obtained by looking up the milliliters of lactose solution titrated in Table 1, mg. (2)
(3)
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)0mL lactose solution is placed on an electric stove and boiled within 2 minutes. After boiling, turn down the flame and keep boiling for 2 minutes. Add 3 drops of methylene blue solution and then continue to drip lactose solution (drop by drop). The end point is when the blue color completely fades away. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration before conversion). 12.1.1.4 Calculate the lactose correction value (f1) of Fehling's solution when determining lactose according to formula (2) and (3): At - ×m× 1000 = 4 ×V, × m250
4×V,×m
actual lactose amount measured, mg,
where: A,\—
Vi——the amount of lactose solution consumed during titration, mL; m
the mass of lactose weighed, g;
the lactose amount obtained by looking up the milliliters of lactose solution titrated in Table 1, mg. (2)
(3)
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)\—
Vi——the amount of lactose liquid consumed during titration, mL; m
the mass of lactose weighed, g;
the amount of lactose obtained by looking up the milliliters of lactose liquid titrated in Table 1, mg. (2)
（3）
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)\—
Vi——the amount of lactose liquid consumed during titration, mL; m
the mass of lactose weighed, g;
the amount of lactose obtained by looking up the milliliters of lactose liquid titrated in Table 1, mg. (2)
（3）
titration amount, ml
GB/T 5413.5--1997
Table 1 Lactose and invert sugar factor table (10mL Fehling's solution) Lactose, mg
Invert sugar.mg
Titration, mL
Lactose, mg
Invert sugar, mg
Note: "The factor refers to the number corresponding to the titration, which can be found in Table 1. If the ratio of sucrose content to lactose content exceeds 3:1, the correction number in Table 2 is added to the titration and then calculated.
12.1.2 Standardization with smoked sugar
12.7.2.1 Weigh about 0.2g (accurate to 0.2mg) of sucrose dried in an oven at 105℃ for 2h, dissolve it in 50mL of water and wash it into a 100ml volumetric flask, add 10mL of water, and then add 10mL of hydrochloric acid (10 .3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the bottle to 67℃ between 2min30s and 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4) and neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool to 20℃, dilute with water to the scale, and shake well. Keep warm at this temperature for 30min and then operate according to 12.1.1.2 and 12.1.1.3. The amount of inverted sugar consumed in titrating 10mL of Fehling's solution is obtained. 12.1.2.2 Calculate the sucrose correction value (f) of Fehling's solution when determining sucrose according to formula (4) and (5): V2 X mz × 1 000
10.5263×V×m2
100 X 0. 95
fs = 10. 5263 XV,Xm
Actual measured inverted sugar number, mg,
Wherein: A2
The amount of sucrose liquid consumed during titration, mL,
-The mass of weighed sucrose, g;
A1.2—The inverted sugar number obtained by looking up the milliliters of sucrose liquid titrated in Table 1, mg. 12.2 Determination of lactose
12.2.1 Sample treatment
..... (4)
（5）
GB/T 5413.5---1997
12.2.1.1 Weigh 2.5~3g sample (accurate to 0.01g), dissolve it several times with 100mL water and wash it into a 250mL volumetric flask. 12.2.1.2 Add 4mL lead acetate (10.6) and 4mL potassium oxalate-sodium hydrogen phosphate solution. Add the reagents slowly each time, shake the volumetric flask, and dilute with water to the scale. Let it stand for a few minutes, filter it with dry filter paper, discard the first 25mL of filtrate, and use the filtrate for titration. 12.2.2 Titration
12.2.2.1 Pre-titration: Inject the filtrate into a 50mL burette for determination. Take 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, heat on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 15s, add 3 drops of methylene blue (10.2), then slowly drip into the lactose solution until the blue color completely fades, read the milliliters of lactose used.
12.2.2.2 Precise titration: Take another 10mL of Fehling's solution (5mL each of solution A and solution B) in a 250mL conical flask, add 20mL of distilled water, add 0.5-1.0mL less lactose solution than the prepared titration amount at a time, put it on an electric stove, let it boil within 2min, turn down the flame after boiling, keep boiling for 2min, add 3 drops of methylene blue solution, then slowly drip into the lactose solution one drop at a time, and the end point is when the blue color completely fades. This titration is used as the basis for calculation (when sucrose is determined at the same time, this is the titration after conversion). 12.2.3 Calculation of lactose content
L = F × fi× 0. 25 × 100
Wherein: L—mass fraction of lactose in the sample g/100gF,—the lactose number obtained by looking up the milliliters of sample solution consumed in Table 1, mg; f.—Fehling's solution lactose correction value;
V,--—volume of filtrate consumed in titration, mL,
m—mass of sample, g.
12.3 Determination of sucrose
12.3.1 Calculation of invert sugar amount before conversion
Using the titration amount when determining lactose, the corresponding invert sugar amount can be found in Table 1 and calculated according to formula (7): F2 × f2X 0.25 × 100
Mass fraction of invert sugar before conversion (%) -: VXm
Wherein: F is the invert sugar amount obtained by looking up the milliliters of sample solution consumed when determining lactose in Table 1, mg; fz
is the sucrose correction value of Fehling's solution;
V. - the amount of filtrate consumed in titration, mL;
- the mass of the sample, 8.
12.3.2 Conversion and titration of sample solution
·(7)
Put 50mL of sample solution in a 100mL volumetric flask, add 10mL of water, then add 10mL of hydrochloric acid (10.3), place in a 75℃ water bath, shake from time to time, and raise the temperature in the flask to 67℃ within 2min30s to 2min45s. After reaching 67℃, continue to keep it in the water bath for 5min, during which time the temperature rises to 69.5℃, take it out, cool it with cold water, and when the temperature in the flask cools to 35℃, add 2 drops of phenol solution (10.4), neutralize it with sodium hydroxide (10.5) until it is neutral, cool it to 20℃, dilute it with water to the mark, and shake it well. Keep it at this temperature for 30min and then titrate it according to 12.2.2 to obtain the amount of conversion solution consumed in titrating 10mL of Fehling's solution. The mass fraction of inverted sugar after conversion (%) F: × fz × 0.50 × 100 V2 X m
Where: F—the number of inverted sugars obtained from V, mg; f2——the sucrose correction value of Fehling's solution;
m-——the mass of the sample, g;
V2--the amount of inverted solution consumed in titration, mL. 12.3.3 Calculation of sucrose content
The sucrose content in the sample (g/100g) = (1, —L,) × 0.95. (8)
. (9)
GB/T5413.5—1997
Where: L, the mass fraction of inverted sugar after conversion, %; L2—the mass fraction of inverted sugar before conversion, %. 12.3.4 If the ratio of lactose to sucrose in the sample exceeds 3:1, the correction value in Table 2 should be added to the titration amount when calculating lactose, and then Table 1 and calculation should be consulted.
12.3.5 Total sugar - sucrose + lactose
13 Allowable difference
13.1 Repeatability
The difference between two results measured by the same analyst within a short time interval should not exceed 1.5% of the average value of the results. 13.2 Reproducibility
The difference between two results measured by two analysts in different laboratories on the same sample should not exceed 2.5% of the average value of the results. Table 2 Correction value of lactose titration
The amount of sugar solution used at the titration endpoint
Same as GB/T 16286.
Method 3
Use 10mL Fehling's solution, sucrose and lactose in a ratio of 3+1
Determination of lactose
(Enzyme colorimetric method)5℃, take it out, cool it with cold water, when the temperature in the bottle cools to 35℃, add 2 drops of methyl red indicator (10.4), neutralize it with 300g/L sodium hydroxide (10.5) until it is neutral. Cool it to 20℃, dilute it to the scale with water, shake it well. Keep it at this temperature for 30 minutes and then operate according to 12.1.1.2 and 12.1.1.3. The amount of invert sugar consumed by titrating 10mL Fehling's solution is obtaine
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